a. Field of the Invention
The present invention pertains generally to processing integrated circuits and specifically to analyzing data from a test vehicle for process improvement and control.
b. Description of the Background
Test vehicles are special integrated circuits that are manufactured on a production line then are carefully analyzed to calculate probable yields and identify any processing problems. Test vehicles may have many different types of patterns that are on the outer limits of the capabilities of the manufacturing process in different ways. In order to most accurately identify processing problems, various test features are often designed into a test vehicle, such making probe points available on the surface of the integrated circuit and arranging the circuitry so that the integrated circuit may be efficiently examined.
Because of the density of devices and traces on today's integrated circuits, the complexity and cost of devices used to test integrated circuits is very high. Further, the production of test vehicles consumes valuable manufacturing time that would otherwise be put to use manufacturing products for sale and revenue. Consequently, the number of test vehicles that can be built and tested is very limited and any data that can come from a particular test vehicle is valuable.
One important set of data that comes from an analysis of a test vehicle is a precise description of an actual failure. Isolating and identifying a failure helps the process engineer fine tune the process and also is critical to developing reliable statistical data about the process. The statistical data are used for estimating yields as well as process refinement.
It would therefore be useful to provide a system and method for obtaining and analyzing test vehicle test data that reliably and efficiently isolates problems and creates reliable and useful data.